Engines may use various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder. One type of fuel delivery uses a port injector for each cylinder to deliver fuel to respective cylinders. Still another type of fuel delivery uses a direct injector for each cylinder.
Further, engines have also been described using more than one injector to provide fuel to a single cylinder in an attempt to improve engine performance. Specifically, in U.S. Pat. No. 2005/0155578 an engine is described using a port fuel injector and a direct injector in each cylinder of the engine.
Another approach utilizing multiple injection locations for different fuel types is described in the papers titled “Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection” and “Direct Injection Ethanol Boosted Gasoline Engine Biofuel Leveraging for Cost Effective Reduction of Oil Dependence and CO2 Emissions” by Heywood et al. Specifically, the Heywood et al. papers describes directly injecting ethanol to improve charge cooling effects, while relying on port injected gasoline for providing the majority of combusted fuel over a drive cycle.
However, the inventors herein have recognized a problem with such approaches, specifically with respect to compensating for variation of components, such as fuel injectors, over. For example, each injector may degrade in different ways over time, and with different effects on fuel injection. Further, such variation can be masked by errors or variation in fuel vapor purge quantities, blends, or concentrations. Further still, depending on the blend or concentration of fuel vapors, different adjustment between injectors may be needed to maintain the desired mixture or blend in the combustion chambers. Finally, in the case where multiple fuel reservoirs are stored on-board a vehicle, different evaporation rates, vapor pressures, temperature, etc. among the different reservoirs can lead to unknown fuel vapor concentrations, flow rates, etc.
In order to compensate for at least some variation of components, a method for controlling engine operation of an engine having a cylinder receiving fuel from a first and a second fuel injector, the first injector having a first relationship between a first input signal and a first amount of injected fuel, and the second injector having a second relationship between a second input signal and a second amount of injected fuel; the method comprising:
varying injection from the first injector into the cylinder;
varying injection from the second injector into the cylinder;
purging fuel vapors from a fuel system into the cylinder; and adaptively learning said first and second relationships based on sensed operating conditions.
In this way, it is possible to utilize difference in injector operation among operating conditions to assign learned information to an appropriate injector.
In another example, a system for an engine of a vehicle traveling on the road,
a first fuel injector coupled to a cylinder of the engine;
a second fuel injector coupled to said cylinder of the engine;
a fuel vapor purge valve configured to delivery vapors to said cylinder of the engine; and
a controller for varying an amount of injection from one of said first and second fuel injectors as a concentration or blend of said vapors varies.
In this way, it is possible to maintain a desired relative amount between the first and second fuel injectors even during variation in concentration or blend of inducted fuel vapors. Therefore, it is possible to maintain a desired boost level, desired torque, desired air-fuel ratio, or others amidst variation in purging conditions by taking advantage of multiple fuel injectors for the cylinder.
In still another example, a system for an engine of a vehicle traveling on the road,
a first fuel injector coupled to a cylinder of the engine;
a second fuel injector coupled to said cylinder of the engine;
a first fuel vapor purge valve configured to adjust delivery vapors from a first reservoir to said cylinder of the engine;
a second fuel vapor purge valve configured to adjust delivery vapors from a second reservoir to said cylinder of the engine, where said second reservoir holds a fuel differing from a fuel in said first reservoir;
a controller for varying an amount of injection from one of said first and second fuel injectors as a concentration or blend of vapors delivered to the engine varies, where at least under some conditions, said first valve enables delivery of vapors from said first reservoir while said second valve restricts delivery of vapors from said second reservoir.
In this way, different reservoirs may be purged differently to account for different conditions among the reservoirs.